I avoid MSG because it makes mammals overeat and become obese. I consider that a sufficient reason. If I am going to get fat I want cookies or ice cream or key lime pie to be involved. I don’t want to get fat eating an additive that may also cause headaches.

However if you want another reason, this mom seemed to find that her autistic daughter had chemical sensitivities underlying her autism. Now these chemical sensitivities are not new and all fit in well to the hypothesis that we have damaged our bionome and that this is what is causing our modern epidemics including certain forms of autism. When she removed MSG (after first removing gluten and casien) her daughter improved.

So I went looking for some evidence that this might be true. As it turns out they just did a mouse study that indicated the MSG and aspartame can adversely impact brain function and cognition in mice.
http://www.ncbi.nlm.nih.gov/pubmed/24556450

And they have know for a while that glutamate activity can play a role in seizures
http://www.ncbi.nlm.nih.gov/pubmed/7970002

That said, I did not find any compelling evidence that removing MSG vs removing glutamates would cure autism. It is also worth noting that she had already removed gluten and dairy. When we discuss salicylates I can carpet bomb you with credible evidence and a theory as to why it happens coming out of teaching hospitals. The microbiome loses its ability to break down salicylates which are everywhere and then these compounds get to the brain. Glutamates (natural and man-made) do seem to affect sensitive individuals, however I cannot find anything that would indicate that MSG removal would cure autism but that it is still OK to eat meat or soy sauce or mushrooms. If you can’t digest glutamates, you can’t digest glutamates.

If you are interested in reading what this mom had to say the article can be found here
http://www.sfgate.com/health/article/Chemist-says-omitting-MSG-cured-daughter-s-autism-5329126.php#page-2

In the end, I would get rid of MSG anyway, but not because I think it will cure autism. MSG has no nutritional value and makes people overeat and can cause headaches. For me that is reason enough.